As an image sensor to be built in a mobile electronic device or a tablet terminal, a solid-state imaging element is widely known. Such a solid-state imaging element has a light receiving surface on which pixels, each including a semiconductor chip or the like and a photoelectric conversion element provided thereon, are arrayed. An image of light provided from an imaging target is formed at the light receiving surface by an optical system such as a lens or the like, and the light of the image is converted into an amount of charges in accordance with the brightness thereof to provide an electric signal. Thus, an output image is provided.
Recently, mobile electronic devices have been progressively reduced in size and improved in quality and functionality. Therefore, a solid-state imaging device mountable on such an electronic device is also desired to be more compact and higher in quality and functionality.
For example, Japanese Laid-Open Patent Publication No. 2012-222546 discloses a solid-state imaging device including a solid-state imaging element mounted on a substrate, a bonding wire electrically connecting a pad provided on the solid-state imaging element and a lead provided on the substrate to each other, a frame member surrounding sides of the solid-state imaging element, and a light-transmissive optical member attached to the frame member while facing an imaging surface of the solid-state imaging element. The frame member includes a leg extending from the optical member side toward the imaging surface. In the state where an end of the bonding wire connected with the pad is covered with the leg, the frame member and the solid-state imaging element are integrally secured to each other.
In order to form an image of the imaging target at the same focal plane on the entirety of the light receiving surface of the solid-state imaging element, it is necessary that an optical axis of a lens group included in a lens unit and normal to the solid-state imaging element match each other. In the above-described structure, one same substrate is used as a reference surface on which the lens unit is attached and as a reference surface on which the solid-state imaging element is attached. However, the flatness of the substrate is not described. In the case where, for example, a glass epoxy substrate is used as the substrate, a complicated process is required to assemble the lens unit and the solid-state imaging element in consideration of the flatness of the surface of the substrate. The complicated process includes making the light receiving surface of a semiconductor chip, which is the solid-state imaging element to be bonded and thus secured to the substrate, parallel with high precision, and making the optical axis of the lens unit perpendicular, with high precision, to the surface of the substrate for securing the lens unit. Due to such a complicated process, the optical axis of the lens group included in the lens unit and the normal to the solid-state imaging element may be undesirably shifted from each other.